Ophthalmic lenses are formed from materials such as glass and transparent plastics. Some of the plastics that are used for the manufacture of ophthalmic lenses include thermoplastic polycarbonate and thermoset materials such as CR-39™, Finalite™ (a registered trademark of Sola International Inc.) and Spectralite™ (a registered trademark of Sola International Inc.).
It has become customary to coat ophthalmic lenses with coatings to provide an improvement in properties. For example, abrasion resistant coatings are used to form a hard coating on an ophthalmic lens, whilst anti-reflection coatings including a hydrophobic surface are used to reduce residual reflections. The hydrophobic surface in the latter coatings makes the surface of the anti-reflection coating easier to clean, as it is easier to remove greasy markings or stains such as those caused by touching the lens. A range of ophthalmic lenses having a hard (abrasion resistant) coating, an anti-reflection coating and a hydrophobic topcoat are now available commercially.
Protective coatings are generally used to protect one or more surfaces (or coatings thereon) of a lens during the normal shipping, handling and processing steps that occur after lens manufacture. Usually, once the lens has reached its destination, the protective coating is removed to reveal a lens surface that is relatively unaffected by the shipping, handling and processing steps. Protective coatings can also be used to mask a surface of a lens during post processing steps. For example, there is often a need to carry out further processing steps on the edge of a lens after lens manufacture without affecting the front or back surfaces of the lens. In this case, protective coatings are used to mask the front and/or back surface of the lens to prevent alteration or damage during the edge treatment. An example of an edge treatment where protective coatings may be used is edge coloring wherein a lens edge may need to be coated with a colored coating for aesthetic purposes. During application of the edge coating, the lens surface needs to be protected to prevent inadvertent application of the colored coating material to the optical surface of the lens.
An example of a temporary protective coating is disclosed in French patent application FR2860303, wherein a peelable film is adhered electrostatically to an outer layer of an optical lens. The outer layer is an anti-slip inorganic layer that is mechanically damaged or removed by friction and/or contact. In this case, the inorganic layer provides anti-slip properties to enable the lens to be edged, whilst the peelable film protects the anti-slip layer from inadvertent damage or removal by friction during normal transport and handling.
However, the use of hydrophobic topcoats on ophthalmic lenses has led to problems with the use of protective coatings on lenses. More specifically, there have been difficulties associated with protective coatings not adhering sufficiently to the hydrophobic topcoats, so that the protective properties of the coating may be compromised.
To the best of the Applicant's knowledge there is no removable coating for a hydrophobic surface of a lens element that is robust enough for normal handling of the lens element, and that does not interfere with further processing such as power checks, marking, edging and edge colouring. The present invention aims to provide a coating that overcomes or reduces at least one of the problems with known coatings and processes.
Throughout this specification reference may be made to documents for the purpose of describing various aspects of the invention. However, no admission is made that any reference cited in this specification constitutes prior art. In particular, it will be understood that the reference to any document herein does not constitute an admission that any of these documents forms part of the common general knowledge in the art in any country. The discussion of the references states what their authors assert, and the applicant reserves the right to challenge the accuracy and pertinency of any of the documents cited herein.